We give references to some of our work on the properties and evolution of the neutral gas component of the Universe (see reference list). The bulk of the observed neutral gas has been detected by identifying intervening damped Lyα (DLA) quasar absorption-line systems with N(H) \u3e 2 × 1020 atoms cm −2. We also present some initial results from a program to identify DLA absorbers near redshift z = 0.5 using Hubble Space Telescope ACS prism spectr
